The invention relates to a smart control strategy for regulating a temperature controller for supplying or exhausting heat to/from a room, object or fluid.
No such smart regulating control strategy was known hitherto. What is known are self-optimizing control systems for regulating room heating, requiring, however, the user to first input a wealth of information as to nature of the heating, the supply flow temperature, the heat losses for various indoor and outdoor temperatures, and so on. It is especially in the case of systems very slow to react, such as those used as a rule in domestic heating systems, as well as in initiating changed setpoint temperatures, that these self-optimizing closed-circuit controllers are unable to prevent a relatively strong overshoot or undershoot of the setpoint temperature. Aside from this, presetting the control parameters is often a highly complicated business in some cases and necessitates much trial and error before arriving at a satisfactory result in functioning.
Also known, of course, are thermostats for regulating living room heating radiators which signal the heating ON/OFF, e.g., via a valve or a circulating pump as soon as a critical setpoint temperature is violated. The ON/OFF hysteresis is usually of the order of 0.5 to 1xc2x0 C., even as much as 2xc2x0 C. in the case of unsophisticated radiator thermostat valves. It is this ON/OFF response of such thermostat regulators that results in room temperature fluctuating seriously, due to the heating system not being able to instantly react to the control signals of the regulator, but only after a considerable delay. Should the thermostat signal the heating OFF, for example, the radiators which are still hot at this time will continue to radiate heat to the surrounding room for quite a few minutes, thus resulting in room temperature significantly increasing above the setpoint temperature. In the reverse situation, when the regulator signals the heating back ON, it will take quite some time until the radiators again become hot, and during this time room temperature drops even further below the setpoint temperature.
This overshoot/undershoot nuisance is aggravated furthermore by the relatively wide hysteresis of thermostatic regulators inherent in their design.
It is on the basis of that said above that the object of the invention is to define a smart control strategy having no need of prior information as to the nature of the heating or cooling required, as to the ambient conditions, especially as regards the temperature losses between the room, object or fluid to be heated and the colder surroundings or, respectively, as regards the heat transfer from the higher temperature surroundings to the room, object or fluid to be cooled, and which not only assures the setpoint temperature desired by the user being maintained very accurately, but also permits speedy achievement of this setpoint temperature with no serious overshoot/ undershoot thereof. In addition to this, the strategy is also intended for use with or facilitated retrofitting to existing heating or cooling systems.
This object is achieved, for one thing, by a smart control strategy for regulating a temperature controller for supplying or exhausting heat to/from a room, object or fluid in which a maximum temperature setpoint (setpoint-MAX) and a minimum temperature setpoint (setpoint-MIN) is specified and the time profile of the actual temperature of the room, object or fluid is regularly measured, comprising the following steps:
defining an nth ON point in time (t-ON(n)) at which the temperature controller is to be signaled ON,
defining an nth OFF point in time (t-OFF(n)) at which the temperature controller is to be signaled OFF,
sensing the two nth extreme values (actual-MAX(n) and actual-MIN(n)) resulting after ON of the temperature controller in the actual temperature profile in which the actual temperature has a local minimum and a local maximum,
determining the 1st derivation of the time profile with time in the nth ON point in time (t-ON(n)),
determining the optimum nth ON/OFF points in time (t-optON(n) and t-optOFF(n)) from the values of the nth OFF point in time (t-OFF(n)) and the nth ON point in time (tON(n)), the two nth extreme values (actual-MAX(n) and actual-MIN(n)) in the temperature profile and the 1st derivation of the temperature profile with time in the nth ON point in time (t-ON(n)) at which for the nth extreme value (actual-MAX(n)) a local maximum in the temperature profile equaling the specified maximum temperature setpoint (setpoint-MAX(n)) and for the nth extreme value (actual-MIN(n)) a local minimum in the temperature profile equaling the specified minimum temperature setpoint (setpoint-MIN(n)) is attained,
incrementing n by 1 and repeating the steps a) to f) taking into account the determined nth ON/OFF points in time (t-optON(n) and t-optOFF(n)) as well as the 1st derivation of the temperature profile with time in the nth ON point in time (t-ON(n)) in establishing the n+1 ON/OFF points in time (t-ON(n+1) and t-OFF(n+1)).
The gist of the invention is thus based on the fact that the temperature of any room, object or fluid to be heated or cooled will always dither about the actually desired setpoint due to the inertia of the heating or cooling system and due to ambient losses. Whilst in the case of simple thermostats only one setpoint is specified which when exceeded results in the heating being signaled OFF and when no longer attained results in the heating being signaled ON, in the control strategy in accordance with the invention two setpoints are specified. These two setpoints mark the maximum swing of the dither about the temperature value as lastly desired, thereby automatically sensing the reaction of the room, object or fluid to a heating or cooling action and taking it into account when the heating or cooling system is next signaled ON. The strategy thus learns the parameters needed for optimum regulation of the corresponding temperature controller without the user having to specify them beforehand. Should the strategy xe2x80x9cseexe2x80x9d for instance that a radiator is still giving off relatively too much heat to the room to be heated after the OFF signal has been given, resulting in the actual temperature exceeding the specified maximum setpoint temperature, then the radiator is signaled off correspondingly earlier in the next heating cycle.
One major advantage afforded by the strategy is that it may be put to use for all kinds of temperature control applications, such as e.g. oil, gas, electric heating, hot air fans, heating coils, heating or cooling elements on heating agent/coolant flow, especially cooling elements in refrigerators, cold rooms and air-conditioning facilities, etc. It is also irrelevant for the strategy whether heat needs to be supplied to or exhausted from a room or object, i.e. the strategy can be put to use in the temperature control of houses, industrial buildings, rooms, tents, vehicle interiors, baking ovens, refrigerator rooms, cold stores, refrigerator trailer vehicles, trains and the like since it automatically establishes the ambient parameters needed for optimum regulation.
In one particularly simple embodiment of the control strategy with no change in the setpoints, setpoint-MAX/MIN, the ON point in time t-ON(n+1) (relative to the temperature profile) is set=t-optON(n) and/or the OFF point in time t-OFF(n+1) (again relative to the temperature profile) is set=t-optOFF(n). It is, of course, clear that instead of the relative ON point in time the strategy will work just as well with the absolute ON point in time. In such a case, of course, a constant time factor needs to be added to the values t-optON(n) and t-optOFF(n). In other words, the strategy may be implemented either so that relative optimum ON/OFF points in time are established for the temperature controller, it being good practice to determine the ON point in time of the temperature controller relative to the actual temperature (i.e. e.g. ON at 20xc2x0 C.) and the OFF point in time relative to the ON point in time (i.e. e.g. OFF after 5 min), or to operate with absolute times (i.e. e.g. ON at 12.05 hours, OFF at 12.10 hours, etc.).
The stability of the regulation may be further enhanced by in addition establishing the time interval between the ON point in time (t-ON(n)) and the local minimum (actual-MIN(n)) when the temperature controller is used for heating or, respectively between the ON point in time t-ON(n+1) and the local maximum (actual-MAX(n)) when the temperature controller is used for cooling. This time interval is additionally taken into account when defining the n+1th OFF point in time t-OFF(n+1). For this purpose it is expedient to define the n+1th OFF point in time t-OFF(n+1) so that an ON duration of the temperature controller materializes corresponding to at least the cited time interval multiplied by a correction factor.
In one expedient variant of the control strategy that after ON of the temperature controller at the ON point in time t-ON(n+1), the 1st derivation of the temperature profile is continually sensed with time and the temperature controller is signaled OFF only when
timeout of the defined OFF point in time t-OFF(n) is attained and
a local minimum (actual-MIN(n)) and local maximum (actual-MAX(n)) has occurred in the heating temperature profile and cooling temperature profile respectively, and
the 1st derivation of the temperature profile with time is greater or smaller than a specified value in heating and cooling respectively, and
the actual temperature is greater than the minimum temperature setpoint (setpoint-MIN) or smaller than the maximum temperature setpoint (setpoint-MAX) in heating and cooling respectively.
The control strategy may also be simplified to advantage by doing away with establishing an OFF point in time t-OFF(n), making OFF of the temperature controller dependent only on a local maximum or local minimum being passed, on a certain minimum slope of the temperature curve and on the minimum temperature setpoint being achieved.
For defining the ON point in time t-ON(n+1) in one preferred embodiment of the strategy, at least the three values t-optON(n), t-optON(nxe2x88x921) and t-optON(nxe2x88x922) are arranged in size and median-filtered, i.e. selecting the mean value as the value for t-ON(n+1). Employing such a median-filter has the advantage that any xe2x80x9crenegadesxe2x80x9d are smoothed out whilst, however, sensing actual changes in the ambient conditions and updating the control strategy accordingly. When, e.g., at very low outdoor temperatures a window is opened for a short time, it could happen that the maximum temperature value actual-MAX resulting at the end of the heating cycle fails to approximate the selected setpoint, setpoint-MAX. Alternatively, although the actual value approximates the setpoint, a temperature sensor sensing the actual temperature wrongly signals too low a room temperature due to it being unfortunately located in the vicinity of the open window.
So that brief opening of the window does not result in the room being overheated on the next heating cycle, the at least last three computed optimum ON/OFF points in time are each arranged according to size and the mean value thereof in each case is taken over as the next ON/OFF points in time to thus avoid xe2x80x9crenegadesxe2x80x9d influencing control. Should, however, the ambient conditions change, for instance by there being a sharp drop in temperature, thus actually requiring heating for a longer time to attain the desired setpoint temperatures, then these changed ambient conditions override after but a few cycles depending on the number of the optimum ON/OFF points in time as computed for use in median-filtering. When, e.g., three ON/OFF points in time are each arranged according to size and the mean value selected in each case, then any change in the ambient conditions will already result in the second cycle in a changeover to the correspondingly changed new optimum ON/OFF points in time.
As an alternative or in addition thereto, the strategy may be designed so that a limit value is specified for the 1st derivation of the temperature profile with time which when violated (corresponding to a sudden jump or drop in temperature, e.g. due to a window being opened) results in the values measured thereafter for defining the optimum ON/OFF points in time, until the occurrence of a specifiable condition, especially dropping below an absolute minimum temperature or change in the temperature profile, no longer being taken into account. When the strategy in accordance with the invention is used for room heating control it may be provided that the heating is signaled OFF on a sudden drop in temperature until a minimum in the temperature profile is attained, thus reliably preventing xe2x80x9cheating for the birdsxe2x80x9d.
The strategy may be used to advantage so that the user merely needs to specify one temperature setpoint from which the values of the setpoint-MAX and setpoint-MIN are automatically defined. When the strategy in accordance with the invention is used for heating regulation, all the user needs to specify is the median temperature desiredxe2x80x94as in known methods of controlxe2x80x94from which then the setpoint-MIN and setpoint-MAX values are defined as a function of how sensitive the apparatus are for defining the actual temperature. When, e.g., a temperature sensor is used which is accurate to 0.05xc2x0 C. it is good practice to select the spacing between setpoint-MIN and setpoint-MAX between 0.3 and 0.4 xc2x0 C. This results in room temperature being regulated to an accuracy of xc2x10.15xc2x0 C. or, respectively, xc2x10.2xc2x0 C. about the median setpoint desired by the user, i.e. the more sensitive the temperature sensors used, the more accurate is the control.
In one expedient embodiment of the strategy, it is provided that the setpoints, setpoint MAX and setpoint MIN, as well as the ON/OFF points in time, t-ON(n) and t-OFF(n), defined lastly relative to these setpoints are memorized in a memory unit. When there is a change in the setpoints the memory is checked to see whether ON/OFF points in time are already memorized for the changed setpoints which are then taken over as the ON/OFF points in time for the first cycle of the control strategy with the new setpoints. This embodiment permits a particularly precise achievement of changed setpoint temperatures in the first cycle of the control without the strategy first needing to obtain information as to possible optimum ON/OFF points in time, since these are already memorized.
In one advantageous embodiment of the strategy, t-ON(n) and t-OFF(n) are defined by means of a central analyzer/control unit with which corresponding control commands for signaling the temperature controller ON/OFF are also generated. In this arrangement the control commands are transmitted from the central analyzer/control unit to the temperature controller wireless or wired. In wireless remission it is good practice to make use of commercially available radio transceiver units which have since become very moderate in price and operate preferably at the frequency of 433 MHz released for general applications. In wired transmission it is good practice to make use of wiring already installed, such as e.g. xe2x80x9cbaby phonexe2x80x9d systems.
When the control strategy is employed for regulation of a temperature controller passing a heating agent/coolant flow wherein the temperature of the heating agent or coolant is adjustable, the strategy may be implemented to advantage in defining and setting the difference required between the heating agent/coolant temperature and the actual temperature (termed supply flow temperature (VT) in the following) from the time interval as measured between t-ON(n) and t-OFF(n) (termed ON duration (D(n)) in the following), as well as from the time interval as measured between the local extreme values actual-MAX(nxe2x88x921) and actual-MIN(n)xe2x80x94when the temperature controller is used for heatingxe2x80x94or, respectively, as well as from the time interval as measured between the local extreme values actual-MIN(n) and actual-MAX(n)xe2x80x94when the temperature controller is used for cooling (termed half cycle (HC(n)) in the following), comprising the following steps:
lowering the supply flow temperature (VT) by a fraction (B) and modifying the heating agent/coolant temperature accordingly if the ON duration (D(n)) is smaller than the half cycle (HC(n)) multiplied by a factor (F),
elevating the supply flow temperature (VT) by a fraction (B) and modifying the heating agent/coolant temperature accordingly if the ON duration (D(n)) is greater than the half cycle (HC(n)) multiplied by a factor (F),
redefining the OFF point in time (t-OFF(n+1)) as it reads from the methods described in paragraph xe2x80x9cf)xe2x80x9d on page 3 hereof and on page 4 hereof so that the ON duration (D(n+1)) in case a) is lengthened by the fraction (B) and in case b) is shortened by the fraction (B).
This embodiment of the strategy permits a particularly energy-saving way of heating or cooling due to the coolant not needing to be cooled unduly below the desired median setpoint temperature or, respectively, due to the heating agent not needing to be heated unduly above the desired median setpoint temperature, since all the more energy is wasted the greater the difference between the coolant/heating agent temperature and the desired setpoint temperature.
In one expedient alternative of the control strategy, instead of a half cycle (HC(n)) the time interval between the local maxima (actual-MAX(nxe2x88x921) and (actual-MAX(n)) is measured (termed full cycle (FC(n)) in the following), this full cycle (FC(n)) being taken into account instead of the half cycle (HC(n)) in the strategy as described in the previous paragraph.
In a further expedient alternative the difference required between heating agent/coolant temperature and the actual temperature (termed supply flow temperature (VT) in the following) is defined and set from the continually defined 1st derivation of the temperature profile with time in the heated or cooled room, object or fluid, comprising the steps:
forming the arithmetic mean from the amounts of the defined 1st derivations of the temperature profile with time in the time interval between the temperature extreme values actual-MAX(nxe2x88x921) and actual-MIN(n) (termed median (1) in the following) as well as in the time interval between the temperature extreme values actual-MIN(n) and actual-MAX(n) (termed median (2) in the following),
lowering the supply flow temperature (VT) by a fraction (B) and modifying the heating agent/coolant temperature accordingly if median (1) is smaller than median (2) multiplied by a factor (F),
elevating the supply flow temperature (VT) by a fraction (B) and modifying the heating agent/coolant temperature accordingly if median (1) is greater than median (2) multiplied by a factor (F),
redefining the OFF point in time (t-OFF(n+1)) as it reads from claims 1 and 2 so that the ON duration (D(n+1)) in case b) is lengthened by the fraction (B) and in case c) is shortened by the fraction (B).
As an alternative to the above a fixed value may be specified instead of the arithmetic mean from the 1st derivations of the temperature profile with time (median (1)).
The control strategy may be put to use advantageously when it is not the heating agent/coolant temperature but the heating/cooling power that is to be regulated, this being particularly the case when the temperature controller is electrically powered. In this case the control strategy as described is put to use with the modification that instead of the difference between heating agent/coolant temperature and the actual temperature (i.e. the supply flow temperature (VT)) it is the heating power in each case that is elevated or lowered.
Defining the heating agent/coolant temperature or the heating/cooling power may be done to advantage by means of a central analyzer/control unit by means of which also corresponding control commands for setting the heating agent/coolant temperature or the heating/cooling power may be generated and transmitted to the temperature controller wireless or wired.